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Principles Related to Practical Chemistry: Chemistry | JEE Main

Q: Why are chromate, iodide, and sulphate considered confirmatory tests?

They form distinct insoluble precipitates (yellow , yellow , and white ) when their respective reagents are added to solution.

Formation of which complex, among the following, is not a confirmatory test of

\text{Pb}^{2+}

ions

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Alead chromateBlead iodideClead nitrateDlead sulphate

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Correct answer

Lead nitrate is highly soluble in water and does not form a precipitate, making it unsuitable as a confirmatory test for $\text{Pb}^{2+}$ .

Option analysis

Why each option works or fails

A · lead chromate

Believing lead chromate is not a confirmatory test because it is confused with other yellow precipitates. Addition of potassium chromate ( $\text{K}_2\text{CrO}_4$ ) yields a characteristic yellow precipitate of $\text{PbCrO}_4$ , which serves as a standard confirmatory test for $\text{Pb}^{2+}$ .

B · lead iodide

Overlooking the distinctive golden spangles test formed by lead iodide. Addition of potassium iodide ( $\text{KI}$ ) produces a bright yellow precipitate of $\text{PbI}_2$ that dissolves in hot water and recrystallizes as golden spangles, confirming $\text{Pb}^{2+}$ .

C · lead nitrate

Correct choice: Recognized that lead nitrate cannot serve as a precipitation-based confirmatory test. All common metal nitrates, including $\text{Pb(NO}_3)_2$ , are soluble in water; hence, adding a nitrate source does not produce a characteristic precipitate to confirm $\text{Pb}^{2+}$ .

D · lead sulphate

Assuming lead sulphate is too soluble to be used as an analytical confirmatory test. Addition of dilute $\text{H}_2\text{SO}_4$ or soluble sulfate yields a white precipitate of $\text{PbSO}_4$ , which dissolves in ammonium acetate, confirming $\text{Pb}^{2+}$ .

Reviewed route

Solution

StepWorking

01concept

A confirmatory test in qualitative inorganic analysis relies on forming an insoluble precipitate with a characteristic color or a distinct observable change. Highly water-soluble, colorless salts cannot serve as precipitate-based confirmatory tests.

02option_verdict

Lead chromate ( $\text{PbCrO}_4$ ) is a bright yellow precipitate formed with potassium chromate ( $\text{K}_2\text{CrO}_4$ ), which confirms the presence of $\text{Pb}^{2+}$ .

03option_verdict

Lead iodide ( $\text{PbI}_2$ ) is a characteristic yellow precipitate formed with potassium iodide ( $\text{KI}$ ), giving the 'golden spangles' test on boiling and cooling to confirm $\text{Pb}^{2+}$ .

04option_verdict

Lead nitrate ( $\text{Pb(NO}_3)_2$ ) is highly soluble in water and forms a clear, colorless solution; hence it cannot serve as a confirmatory precipitate test for $\text{Pb}^{2+}$ .

05option_verdict

Lead sulphate ( $\text{PbSO}_4$ ) is a white precipitate formed with dilute $\text{H}_2\text{SO}_4$ , soluble in ammonium acetate, confirming the presence of $\text{Pb}^{2+}$ .

✓discriminator

All common nitrate salts, including $\text{Pb(NO}_3)_2$ , are soluble in water and do not form precipitates, making lead nitrate the only non-confirmatory compound among the options.

Hints that build this answer step by step

What physical phenomenon typically indicates a positive confirmatory test for $\text{Pb}^{2+}$ in qualitative inorganic analysis?
The formation of an insoluble, distinctly colored or characteristic precipitate
Which of the four compounds is freely soluble in cold water and therefore cannot form a confirmatory precipitate?
Lead nitrate

✓ Source and academic review

Question type: Single correct
Exam relevance: JEE Main · Chemistry
Concepts assessed: Chemistry
Academic status: Reviewed by official_key
Source: pyq
Editorial review: 9 September 2026

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Students also ask

Why are chromate, iodide, and sulphate considered confirmatory tests?

They form distinct insoluble precipitates (yellow $\text{PbCrO}_4$ , yellow $\text{PbI}_2$ , and white $\text{PbSO}_4$ ) when their respective reagents are added to $\text{Pb}^{2+}$ solution.

Answer

Lead nitrate is highly soluble in water and does not form a precipitate, making it unsuitable as a confirmatory test for $\text{Pb}^{2+}$ .

Why each option works or fails

A: lead chromate - Believing lead chromate is not a confirmatory test because it is confused with other yellow precipitates. Addition of potassium chromate ( $\text{K}_2\text{CrO}_4$ ) yields a characteristic yellow precipitate of $\text{PbCrO}_4$ , which serves as a standard confirmatory test for $\text{Pb}^{2+}$ .
B: lead iodide - Overlooking the distinctive golden spangles test formed by lead iodide. Addition of potassium iodide ( $\text{KI}$ ) produces a bright yellow precipitate of $\text{PbI}_2$ that dissolves in hot water and recrystallizes as golden spangles, confirming $\text{Pb}^{2+}$ .
C · correct: lead nitrate - Correct choice: Recognized that lead nitrate cannot serve as a precipitation-based confirmatory test. All common metal nitrates, including $\text{Pb(NO}_3)_2$ , are soluble in water; hence, adding a nitrate source does not produce a characteristic precipitate to confirm $\text{Pb}^{2+}$ .
D: lead sulphate - Assuming lead sulphate is too soluble to be used as an analytical confirmatory test. Addition of dilute $\text{H}_2\text{SO}_4$ or soluble sulfate yields a white precipitate of $\text{PbSO}_4$ , which dissolves in ammonium acetate, confirming $\text{Pb}^{2+}$ .

Step-by-step solution

concept: A confirmatory test in qualitative inorganic analysis relies on forming an insoluble precipitate with a characteristic color or a distinct observable change. Highly water-soluble, colorless salts cannot serve as precipitate-based confirmatory tests.
option_verdict: Lead chromate ( $\text{PbCrO}_4$ ) is a bright yellow precipitate formed with potassium chromate ( $\text{K}_2\text{CrO}_4$ ), which confirms the presence of $\text{Pb}^{2+}$ .
option_verdict: Lead iodide ( $\text{PbI}_2$ ) is a characteristic yellow precipitate formed with potassium iodide ( $\text{KI}$ ), giving the 'golden spangles' test on boiling and cooling to confirm $\text{Pb}^{2+}$ .
option_verdict: Lead nitrate ( $\text{Pb(NO}_3)_2$ ) is highly soluble in water and forms a clear, colorless solution; hence it cannot serve as a confirmatory precipitate test for $\text{Pb}^{2+}$ .
option_verdict: Lead sulphate ( $\text{PbSO}_4$ ) is a white precipitate formed with dilute $\text{H}_2\text{SO}_4$ , soluble in ammonium acetate, confirming the presence of $\text{Pb}^{2+}$ .
discriminator: All common nitrate salts, including $\text{Pb(NO}_3)_2$ , are soluble in water and do not form precipitates, making lead nitrate the only non-confirmatory compound among the options.

Principles Related to Practical Chemistry: Chemistry | JEE Main

What feels right?

Lead nitrate is highly soluble in water and does not form a precipitate, making it unsuitable as a confirmatory test for $\text{Pb}^{2+}$ .

Why each option works or fails

Solution

01concept

02option_verdict

03option_verdict

04option_verdict

05option_verdict

✓discriminator

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Principles Related to Practical Chemistry: Chemistry | JEE Main

Lead nitrate is highly soluble in water and does not form a precipitate, making it unsuitable as a confirmatory test for Pb2+\text{Pb}^{2+}Pb2+.

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Lead nitrate is highly soluble in water and does not form a precipitate, making it unsuitable as a confirmatory test for $\text{Pb}^{2+}$ .